I was able to reproduce the error using a fresh build from tip (34d5ec8a1019):

/tmp/test$ PYTHON=/opt/python3.3/bin/python3 ./test.sh
['__main__', '_bisect', '_codecs', '_collections', '_frozen_importlib', '_functools', '_heapq', '_imp', '_io', '_locale', '_sre', '_sysconfigdata', '_thread', '_warnings', '_weakref', '_weakrefset', 'abc', 'bisect', 'builtins', 'codecs', 'collections', 'collections.abc', 'copyreg', 'encodings', 'encodings.aliases', 'encodings.latin_1', 'encodings.utf_8', 'errno', 'functools', 'genericpath', 'heapq', 'io', 'itertools', 'keyword', 'locale', 'marshal', 'operator', 'os', 'os.path', 'posix', 'posixpath', 're', 'reprlib', 'signal', 'site', 'sre_compile', 'sre_constants', 'sre_parse', 'stat', 'sys', 'sysconfig', 'weakref', 'zipimport']
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "__init__.py", line 11, in init my_test_package (my_test_package/__init__.c:1106)
SystemError: Parent module 'my_test_package' not loaded, cannot perform relative import